Method of making thiol methacrylate or acrylate and a lens made therefrom

ABSTRACT

A thiol methacrylate or acrylate compound represented by the formula (1) or (2): ##STR1## wherein R 1  is H or CH and X is selected from: ##STR2## wherein R 1  is H or CH 3  and m is an integer of 1 to 4. The thiol methacrylate or acrylate compound gives a resin having a high refractive index, a large Abbe number, and a good hardness and heat resistance, and giving little or no smell at processing.

This application is a division of application Ser. No. 08/169,603, filedon Dec. 17, 1993, now U.S. Pat. No. 5,399,735, which is a division ofapplication Ser. No. 08/001,075, filed on Jan. 6, 1993, now U.S. Pat.No. 5,294,690, which is a continuation of prior application Ser. No.07/844,477 filed on Mar. 2, 1992, now U.S. Pat. No. 5,247,041, which isa continuation of prior application Ser. No. 07/482,285 filed Feb. 20,1990, now abandoned.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a novel thiol (meth)acrylate, a resinformed from this (meth)acrylate and a high-refractive-index plastic lenscomposed of this resin.

2. Description of the Related Art

Olefinic thermosetting resins generally have an excellent heatresistance and chemical resistance, and especially, a resin composed ofdiallyl phthalate is widely used on an industrial scale because of itsexcellent heat resistance and chemical resistance and good dimensionalstability. In some application fields, higher dimensional stability orchemical resistance and reduced water-absorbing characteristics,however, are required.

Diethylene glycol bisallyl carbonate is often applied to optical uses.However, the diethylene glycol bisallyl carbonate used for opticalarticles has a problem in that the refractive index is low.

For eliminating this disadvantage, there have been proposed thiol(meth)acrylates, for example, resins composed mainly of an aromaticthiol ester (Japanese Unexamined Patent Publication No. 63-316766), andan aliphatic thiol ester (U.S. Pat. No. 4,810,812) and JapaneseUnexamined Patent Publication No. 63-188660).

Resins proposed in Japanese Unexamined Patent Publication No. 63-316766,U.S. Pat. No. 4,810,812, and Japanese Unexamined Patent Publication No.63-188660 still have a problem in that optical characteristics having agood balance between a high refractive index and a large Abbe numbercannot be obtained. Furthermore, these resins emit a strong offensivesmell at the time of processing such as cutting or polishing. Moreover,since these resins are solid at normal temperature, cast polymerizationcannot be performed at normal temperature, and the resins have a poorhardness and heat resistance.

SUMMARY OF THE INVENTION

The present invention is to solves the above-mentioned problems of theconventional techniques, and a primary object of the present inventionto provide a thiol (meth)acrylate valuable as a monomer for theproduction of a resin which has a high refractive index and a large Abbenumber, gives little or no smell at processing and has excellenthardness and heat resistance; a resin composed of this monomer; and ahigh-refractive-index lens formed of this resin.

In accordance with the present invention, there is provided a thiolmethacrylate or acrylate compound represented by the following formula(1) or (2): ##STR3## wherein R¹ represents a hydrogen atom or a methylgroup and X represents a divalent group selected from the groupconsisting of: ##STR4## wherein R¹ is the same as defined above and m isan integer of from 1 to 4.

The present invention further provides a thiol methacrylate or acrylateresin prepared by polymerizing the thiol methacrylate or acrylatecompound of the formula (1) or (2) or a monomer mixture comprising atleast 10% by weight of at least one of the thiol methacrylate oracrylate compounds of the formula (1) or (2).

The present invention further provides a high-refractive-index plasticlens composed of the above-mentioned thiol methacrylate or acrylateresin.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a chart of the infrared absorption spectrum of the compound ofExample 1 of the present invention;

FIG. 2 is a chart of the infrared absorption spectrum of the compound ofExample 3 of the present invention; and

FIG. 3 is a chart of the infrared absorption spectrum of the compound ofExample 5 of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The compound of the present invention represented by the formula (1)wherein X is the divalent group of the formula (a) can be synthesized byreacting a divalent mercaptan compound (D), synthesized through asynthesis scheme passing through compounds represented by the followingformulae (A) through (C), with a (meth)acrylic acid halide in thepresence of an alkali such as a metal hydroxide or a tertiary amine:##STR5##

The compound of the present invention, represented by the formula (1)wherein X is the divalent group the formula (b) can be synthesized byreacting a mercaptan compound (G), synthesized through a synthesisscheme passing through compounds represented by the following formulae(E) and (F), with a (meth)acrylic acid halide in the presence of analkali such as a metal hydroxide or a tertiary amine: ##STR6##

The compound of the present invention, represented by the formula (1)wherein X is the divalent group of the formula (c) can be synthesized byreacting a trivalent mercaptan compound (J), synthesized through asynthesis scheme passing through compounds represented by the followingformulae (H) and (I), with a (meth)acrylic acid halide in the presenceof an alkali such as a metal hydroxide or a tertiary amine: ##STR7##

The compound of the present invention represented by the formula (2) canbe synthesized in a manner similar to the compound of the formula (1)wherein X is the divalent radical of the formula (b), except that amercaptan compound (M) is synthesized through a synthesis scheme passingthrough compounds represented by the following formulae (K) and (L), andis then reacted with a (meth)acrylic acid halide. ##STR8##

Especially, if a tertiary amine in an amount of 3 to 95 molarequivalents to the --SH group and a metal hydroxide in an amount of 5 to120 molar equivalents to the --SH group are used in combination as thedehydro-chlorinating agent for forming the thiol (meth)acrylate monomer,the purity and yield of the monomer can be increased.

A resin having an excellent transparency can be prepared byincorporating 0.001 to 5 parts by weight of a radical polymerizationinitiator such as a peroxide or azo type initiator customarily used forthe radical polymerization in 100 parts by weight of the thiol(meth)acrylate monomer or a monomer mixture comprising at least 10% byweight of the thiol (meth)acrylate monomer and polymerizing the monomeror monomer mixture by application of heat or irradiation with light. Inthis case, a monomer other than the thiol (meth)acrylate of the presentinvention can be copolymerized with the thiol (meth)acrylate.

In this copolymerization, in view of the characteristics of the obtainedresin, at least one monomer selected from the group consisting ofmonomers represented by the formulae (1) and (2) according to thepresent invention is preferably used in an amount of at least 10% byweight.

Olefinic compounds can be used as the comonomer to be added without anyparticular limitation. (Meth)acrylic compounds, styrene compounds,acrylonitrile and N-phenylmaleimide are preferably used. As specificexamples, there can be mentioned methyl (meth)acrylate, ethyl(meth)acrylate, propyl (meth)acrylate, benzyl (meth)acrylate, phenyl(meth)acrylate, cyclohexyl (meth)acrylate, cyclohexylmethylene(meth)acrylate, styrene, vinylnaphthalene, halogen-substituted styrene,α-methylstyrene, divinylbenzene, diallyl phthalate, ethylene glycoldi(meth)acrylate, bisphenol A di(meth)acrylate, bisphenol A dihydroxyethyl (meth)acrylate!, tetrabromobisphenol A di(meth)acrylate,tetrabromobisphenol A di hydroxyethyl (meth)acrylate!, triallylisocyanurate, pentaerythritol tetrakis(meth)acrylate, diethylene glycolbisallyl carbonate, and compounds represented by the following formula(N): ##STR9## wherein R² represents a hydrogen atom or a methyl group.

The compound represented by the formula (N) can be synthesized byreacting a dithiol represented by the following formula (O): ##STR10##with (meth)acrylic acid chloride in the presence of an alkali such as ametal hydroxide or a tertiary amine.

When the compound represented by the formula (N) is homopolymerized, aresin having a refractive index of 1.69 is obtained, and the specificgravity of the resin is as low as 1.23. Since the resin is solid atnormal temperature, when a polymer is obtained by the castpolymerization, copolymerization with another monomer is carried out,whereby a polymer having well-balanced optical characteristics can beobtained.

If a polyfunctional thiol compound is added as the copolymerizationcomponent in addition to the above-mentioned olefinic compound, a resinhaving an excellent processability can be obtained. As thepolyfunctional thiol compound, there can be mentioned pentaerythritoltetrakisthioglycolate, trismercaptopropyl isocyanurate, and compoundsrepresented by the above-mentioned formulae (D), (G), (J) and (O).

To obtain a resin having excellent mechanical characteristics,preferably a monomer mixture comprising 15 to 90% by weight of the thiol(meth)acrylate of the formula (1) or (2) and 10 to 85% by weight ofstyrene can be copolymerized. In this case, up to 75% by weight ofanother olefinic compound as mentioned above except for the thiol(meth)acrylate and styrene can be further copolymerized. Ahalogen-containing or halogen-free di(meth)acrylate having bisphenol Ain the molecule structure can be preferably used as the olefiniccompound.

As the di(meth)acrylate having bisphenol A in the molecule structure,there can be mentioned, for example, compounds represented by thefollowing formula: ##STR11## wherein R³ represents a hydrogen atom or amethyl group.

Various thiol (meth)acrylate monomers represented by the formulae (1)and (2) can be used for the production of the above-mentioned copolymerwithout any limitation, and there can be obtained resins having not onlyexcellent mechanical properties but also excellent opticalcharacteristics such as a high refractive index and a large Abbe number.

To obtain a resin having excellent abrasion characteristics, preferably15 to 90% by weight of at least one thiol (meth)acrylate monomer of theformula (1) or (2) is copolymerized with 10 to 85% by weight of amonomer having both of a urethane bond and a (meth)acryl group in themolecule. In this case, up to 75% by weight of another copolymerizableolefinic compound as mentioned above (except for the thiol(meth)acrylate and the monomer having both of a urethane bond and amethacryl or acryl group in the molecule) can be further copolymerized.

As the monomer having both a urethane bond and a (meth)acryl group inthe molecule, there can be mentioned, for example, monomers having asubstituent represented by the following formula: ##STR12## wherein Yrepresents an alkylene group having 1 to 10 carbon atoms, R⁴ representsa hydrogen atom or a methyl group, and l is an integer of from 0 to 3.

The kind of the thiol (meth)acrylate of the formula (1) or (2) is notparticularly critical, and there can be obtained resins having not onlyexcellent abrasion characteristics but also excellent opticalcharacteristics such as a high refractive index and a large Abbe number.

The cast polymerization is preferably adopted for preparing a resin fromthe thiol (meth)acrylate of the present invention. As a preferredexample of the cast polymerization process, there can be mentioned aprocess comprising casting the thiol (meth)acrylate of the presentinvention or a liquid mixture of the thiol (meth)acrylate with at leastone monomer selected from the above-mentioned copolymerizable monomers,together with a polymerization initiator, into a mold assembly composedof a glass mold or metal mold and an adhesive tape or a plastic gasket,and effecting the polymerization by heating at 30° to 150° C. for 0.1 to40 hours or by irradiation with ultraviolet rays.

In the preparation of a resin from the thiol (meth)acrylate, thepolymerization is preferably effected by using a peroxide initiator suchas benzoyl peroxide, t-butyl peroxyisobutyrate, diisopropylperoxydicarbonate or t-butyl peroxypivalate, whereby a lens having anexcellent appearance can be obtained.

By using the thiol (meth)acrylate of the present invention, a resinhaving a high refractive index, a large Abbe number and an excellenttransparency can be obtained. Furthermore, although the obtained resinis a sulfur-Containing resin, no smell is generated at processing.Moreover, since the thiol (meth)acrylate is a thioester compound, theobtained resin has a lower water absorption and a higher chemicalresistance than those of resins derived from ester compounds.

Moreover, if a lard coat film or a reflection-preventing film is formedon the surface of the obtained resin, an article having a high surfacehardness or an excellent light-transmitting property can be obtained.When the hard coat film or reflection-preventing film is formed, thesurface of the resin substrate can be subjected to a preliminarytreatment such as an alkali treatment or a plasma treatment, whereby theadhesion between the resin substrate and the hard coat film orreflection-preventing film can be improved. As the hard coat film, therecan be mentioned an organic film composed of melamine or aurethane/polyfunctional acrylic resin, a silicon type organic orinorganic film, and an inorganic film containing an antimony pentoxidetype metal oxide.

The present invention will now be described in detail with reference tothe following examples.

EXAMPLE 1

A three-neck flask having an inner volume of 1,000 ml was charged with30 g of a compound represented by the following formula (P): ##STR13##300 g of toluene, 500 g of 1N sodium hydroxide, 1 g of sodiumborohydride and 100 mg of hydroquinone monomethyl ether, and 33 g ofmethacrylic acid chloride was gradually dropped into the mixture innitrogen at 0° C. with stirring. Then, the mixture was stirred at 0° C.for 2 hours. Then, the toluene layer was washed and filtered, and thesolvent was removed by distillation to obtain a compound represented bythe following formula (Q): ##STR14##

The appearance, refractive index and elementary analysis of thiscompound are shown in Table 1. The infrared absorption spectrum chart ofthis compound is shown in FIG. 1.

Since the absorption attributed to --S--CO-- was observed at 1665 cm⁻¹,it was confirmed that the thiol (meth)acrylate represented by theformula (Q) was obtained.

The NMR results of the obtained compound were as shown below: ##STR15##

A solution comprising 99 parts by weight of the above compound and 1part by weight of benzoyl peroxide was cast in a casting mold assemblycomposed of a glass mold and an adhesive tape, and the temperature waselevated from 50° C. to 120° C. over a period of 15 hours to obtain aresin. The properties of the obtained resin are shown in Table 2. Whenthe infrared absorption spectrum was measured, the absorption attributedto CH₂ =C< was not observed at 1620 cm⁻¹. Accordingly, it was confirmedthat a thiol (meth)acrylate resin was obtained.

The heat resistance was evaluated based on the Shore D hardness at 100°C. The sample having a Shore D hardness of less than 50 was indicated bymark "C", the sample having a Shore D hardness of 50 to 70 was indicatedby mark "B", and the sample having a Shore D hardness exceeding 70 andup to 100 was indicated by mark "A".

To examine generation of smell at processing, the sample was polished bya polishing machine and generation of smell was checked. The sample notgenerating any smell was indicated by mark "A", and other sample wasrepresented by mark "C".

The refractive index was measured by a Pulfrlch refractometer. Thetransmission and light resistance were measured by using a colorcomputer and a fadeometer. The light resistance was evaluated after anexposure for 100 hours to a fadeometer, and the sample exhibiting achange in yellowness index (ΔYI) of less than 10 was indicated by mark"A", the sample exhibiting a ΔYI of 10 to 20 was indicated by mark "B",and the sample exhibiting a ΔYI of more than 20 was indicated by mark"C".

EXAMPLE 2

A compound represented by the following formula (R): ##STR16## wasprepared in the same manner as described in Example 1 except thatacrylic acid chloride was used instead of methacrylic acid chloride. Theproperties of the obtained compound were determined in the same manneras described in Example 1. The results are shown in Table 1.

A resin was prepared from this compound in the same manner as describedin Example 1. The properties of the obtained resin are shown in Table 2.

EXAMPLE 3

A compound represented by the following formula (T): ##STR17## wasprepared in the same manner as described in Example 1 except that acompound represented by the following formula (G): ##STR18## was usedinstead of the compound of the formula (P).

The infrared absorption spectrum of the obtained compound is shown inFIG. 2. Since the absorption attributed to --S--CO-- was observed at1665 cm⁻¹, it was confirmed that the compound of the formula (T) wasobtained.

The NMR results of the above compound were as shown below: ##STR19##

A resin was prepared from the obtained compound in the same manner asdescribed in Example 1. The properties of the obtained resin are shownin Table 2. When the infrared absorption spectrum of the obtained resinwas measured, the absorption attributed to CH₂ =C< was not observed at1620 cm⁻¹. Accordingly, it was confirmed that a thiol (meth)acrylateresin was obtained.

EXAMPLE 4

A compound represented by the following formula (S): ##STR20## wasprepared in the same manner as described in Example 1 except that acompound represented by the following formula (M): ##STR21## was usedinstead of the compound (P). The properties of the obtained compoundwere measured in the same manner as described in Example 1. The resultsare shown in Table 1.

A resin was prepared from the obtained compound in the same manner asdescribed in Example 1. The properties of the obtained resin are shownin Table 2.

EXAMPLE 5

A compound represented by the following formula (U): ##STR22## wasprepared in the same manner as described in Example 1 except that acompound represented by the following formula (J): ##STR23## was usedinstead of the compound of the formula (P). The properties of theobtained compound were measured in the same manner as described inExample 1. The results are shown in Table 1.

The infrared absorption spectrum of the obtained compound is shown inFIG. 3. Since the absorption attributed to --S--CO-- was observed at1665 cm⁻¹, it was confirmed that the thiol (meth)acrylate represented bythe formula (U) was obtained.

The NMR results of the obtained compound were as shown below: ##STR24##

A resin was prepared from the compound of the formula (U) in the samemanner as described in Example 1. The properties of the obtained resinare shown in Table 2. When the infrared absorption spectrum of theobtained resin was measured, the absorption attributed to CH₂ =C< wasnot found at 1620 cm⁻¹. Accordingly, it was confirmed that a thiol(meth)acrylate resin was obtained.

EXAMPLE 6

A compound represented by the following formula (V): ##STR25## wasprepared in the same manner as described in Example 1 except that acompound represented by the following formula (O): ##STR26## was usedinstead of the compound of the formula (P). The properties of theobtained compounds were measured in the same manner as described inExample 1. The results are shown in Table 1.

Then, 30 parts of the obtained compound of the formula (V) was mixedwith 70 parts by weight of the compound of the formula (Q) obtained inExample 1, and a resin was prepared from this mixture in the same manneras described in Example 1. The properties of the obtained resin areshown in Table 2.

COMPARATIVE EXAMPLE 1

A three-neck flask having an inner volume of 1,000 ml was charged with20 g of a compound represented by the following formula (α):

    HSCH.sub.2 CH.sub.2 SCH.sub.2 CH.sub.2 SH                  (α)

300 g of toluene, 500 g of 1N sodium hydroxide, 1 g of sodiumborohydride and 100 mg of hydroquinone monomethyl ether, and 33 g ofmethacrylic acid chloride was gradually dropped into the mixture innitrogen at 0° C. with stirring and the mixture was stirred at 0° C. for2 hours. Then, the toluene layer was washed and filtered, and thesolvent was removed by distillation to obtain a compound represented bythe following formula (β): ##STR27## Then, 99 parts by weight of theobtained compound was polymerized in the same manner as described inExample 1 to obtain a resin. The properties of the obtained resin areshown in Table 2.

COMPARATIVE EXAMPLE 2

A compound represented by the following formula (δ): ##STR28## wasprepared in the same manner as described in Comparative Example 1 exceptthat a compound represented by the following formula (γ): ##STR29## wasused instead of the compound of the formula (α).

The obtained compound was polymerized in the same manner as described inExample 1 to obtain a resin. The properties of the obtained resin areshown in Table 2.

COMPARATIVE EXAMPLE 3

A compound represented by the following formula (ξ): ##STR30## wasprepared in the same manner as described in Comparative Example 1 exceptthat a compound represented by the following formula (ε): ##STR31## wasused instead of the compound of the formula (α).

The obtained compound was polymerized in the same manner as described inExample 1 to obtain a resin. The properties of the obtained resin areshown in Table 2.

                                      TABLE 1    __________________________________________________________________________                Refrac-         Elementary    Appear-     tive Elementary analysis                                analysis    ance        index                     (theoretical values)                                (found values)    __________________________________________________________________________    Exam- Color-                1.58 C:H:O:S    C:H:O:S    ple 1 less       48.0:6.3:9.1:36.6                                48.5:6.5:9.0:35.8          trans-          parent          liquid    Exam- Color-                1.59 C:H:O:S    C:H:O:S    ple 2 less       44.7:5.6:9.9:39.8                                44.9:5.9:10.2:39.0          trans-          parent          liquid    Exam- Color-                1.62 C:H:O:S    C:H:O:S    ple 3 less       57.7:3.8:7.7:30.8                                57.6:3.6:7.8:31.0          trans-          parent          liquid    Exam- Color-                1.61 C:H:O:S    C:H:O:S    ple 4 less       61.9:6.3:6.3:25.4                                61.7:6.2:6.3:25.7          trans-          parent          liquid    Exam- Color-                1.59 C:H:O:S    C:H:O:S    ple 5 less       48.0:6.3:9.1:36.6                                47.8:6.2:8.9:37.1          trans-          parent          liquid    Exam- White 1.64 C:H:O:S    C:H:O:S    ple 6 trans-     60.5:5.0:11.5:23.0                                60.3:4.9:11.9:22.8          parent          liquid    __________________________________________________________________________

                                      TABLE 2    __________________________________________________________________________    Heat    Generation                  Refrac-       Light    Casting    resist- of smell at                  tive                      Trans-                           Specific                                resist-                                    Abbe temperature    ance    processing                  index                      mittance                           gravity                                ance                                    number                                         in mold (°C.)    __________________________________________________________________________    Exam-        A   A     1.64                      86   1.29 A   38   20    ple 1    Exam-        A   A     1.65                      88   1.28 A   37   20    ple 2    Exam-        A   A     1.65                      88   1.30 A   34   20    ple 3    Exam-        A   A     1.63                      87   1.26 A   32   20    ple 4    Exam-        A   A     1.64                      86   1.28 A   38   20    ple 5    Exam-        A   A     1.66                      86   1.27 B   33   20    ple 6    Comp.        B   C     1.62                      87   1.33 A   38   20    Ex. 1    Comp.        A   A     1.62                      80   1.31 C   32   60    Ex. 2    Comp.        A   A     1.67                      81   1.26 C   24   80    Ex. 3    __________________________________________________________________________

As shown above, the thiol (meth)acrylate of the present invention has ahigh refractive index, and a resin derived from this thiol(meth)acrylate has a high refractive index and generates little or nooffensive smell of sulfur. Moreover, this resin has a high transparencyand an excellent heat resistance.

Therefore, the compound and resin of the present invention can be widelyused in the fields of paints, electronic parts, and optical articles.

We claim:
 1. A high-refractive-index plastic lens composed of a thiol methacrylate or acrylate resin obtained by polymerizing a thiol methacrylate or acrylate monomer represented by the following formula (1) or (2), or a monomer mixture comprising at least 10% by weight of the thiol methacrylate or acrylate monomer of the formula (1) or (2): ##STR32## wherein R¹ represents a hydrogen atom or a methyl group and X represents a divalent group selected from the group consisting of: ##STR33## wherein R¹ is the same as defined above and m is an integer of from 1 to
 4. 